It is generally known that a wheel bearing apparatus incorporating a wheel speed detecting apparatus can support a vehicle wheel relative to a suspension apparatus and can detect the wheel speed to control the anti-lock braking system (ABS). Such a bearing apparatus generally includes a wheel speed detecting apparatus. The detecting apparatus includes a magnetic encoder with magnetic poles alternately arranged along its circumference and integrated in a sealing apparatus arranged between inner and outer members for containing rolling elements therebetween. A wheel speed detecting sensor detects the variation in the magnetic poles of the magnetic encoder according to the rotation of the wheel.
The wheel speed sensor is usually mounted on a knuckle after the wheel bearing apparatus is mounted on the knuckle to form a suspension apparatus. Recently, a wheel bearing apparatus incorporating a wheel speed detecting apparatus has been proposed where a wheel speed detecting sensor is incorporated into the wheel bearing. Such a device reduces the size of the wheel bearing apparatus as well as eliminates troublesome in air gap adjustment between the wheel speed sensor and the magnetic encoder.
An example of the wheel bearing apparatus incorporating a wheel speed detecting apparatus is shown in FIG. 28. The wheel bearing apparatus incorporating a wheel speed detecting apparatus includes an outer member 101 secured on a suspension apparatus (not shown) of a vehicle forming a secured member. An inner member 102 is inserted into the outer member 101, via a plurality of balls 103, 103. The outer member is integrally formed on its outer circumference with a body mounting flange 101b. The outer member inner circumference includes double row outer raceway surfaces 101a, 101a. 
The inner member 102 includes a wheel hub 105 and an inner ring 106. The wheel hub 105 and inner ring 106 are formed with double row inner raceway surfaces 105a, 106a, respectively, that are positioned opposite to the double row outer raceway surfaces 101a, 101a. One inner raceway surface 105a is formed on the outer circumference of the wheel hub 105 and the other inner raceway surface 106a is formed on the outer circumference of the inner ring. The inner ring 106 is press-fit onto a cylindrical portion 105b that axially extends from the inner raceway surface 105a of the wheel hub 105. Double row balls 103, 103 are contained between these double row outer and inner raceway surfaces. The balls are rollably held by cages 107, 107.
The wheel hub 105 is integrally formed with a wheel mount flange 104 to mount a wheel (not shown). Hub bolts 104a are secured on the flange 104 at circumferentially equidistant positions. The wheel hub 105 is further formed with a serration 105c on its inner circumference. A stem portion 111 of an outer joint member 110, that forms a constant velocity universal joint, is inserted into the serration 105c. Seals 108, 109 are mounted on both ends of the outer member 101. The seals 108, 109 prevent leakage of grease contained within the bearing and the entry of rainwater or dusts from the outside into the bearing.
As shown in FIG. 29, the inner side seal 109 includes a first sealing plate 112. The plate 112 has an L shaped cross-section and is adapted to fit into the inner circumference of the outer member 101. A second sealing plate 113 has an L shaped cross-section and is adapted to be arranged opposite to the first sealing plate 112. The second sealing plate 113 includes a cylindrical portion 113a adapted to fit onto the inner ring 106. A standing portion 113b extends radially outward from the cylindrical portion 113a. A magnetic encoder 114 is adhered to the inner side surface of the standing portion 113b, via vulcanized adhesion. The magnetic encoder 114 is formed from a rubber mingled with magnetic powder. Also, it includes magnetic N and S poles alternately arranged along its circumferential direction.
The first sealing plate 112 includes a metal core 115 with an L shaped cross-section. A sealing member 116 is adhered to the metal core 115, via vulcanized adhesion. The sealing member 116 includes a side lip 116a in sliding contact with the outer side surface of the standing portion 113b of the second sealing plate 113. A pair of radial lips 116b, 116c is in sliding contact with the cylindrical portion 113a of the second sealing plate 113.
An annular sensor holder 119 is mounted on the end of the outer member 101. The annular sensor holder 119 includes a fitting cylinder 117 and a holding portion 118 joined to the fitting cylinder 117. The fitting cylinder 117 includes a cylindrical fitting portion 117a. A flange portion 117b extends radially inward from the fitting portion 117a. The fitting cylinder has a wholly annular configuration with an L shaped cross-section.
The holding portion 118 is integrally molded and embedded with a wheel speed sensor 120. The speed sensor 120 opposes the encoder 114, via a predetermined air gap. The wheel speed sensor 120 includes a magnetic detecting element such as a Hall effect element, magnetic resistance element (MR element) etc. to change its characteristics in accordance with the flow direction of magnetic flux. An IC incorporating a wave forming circuit for rectifying the output wave form of magnetic detecting element is also included.
A labyrinth seal is formed by a small gap 121 between the end face of the inner ring 106 and the flange portion 117b. The labyrinth seal can prevent foreign matter such as magnetic powder etc. from entering into a space between the magnetic encoder 114 and the wheel speed sensor 120 before the stem portion 111 of the outer joint member 110 is inserted into the wheel hub 105. This includes transportation of the bearing apparatus to an assembling line of a manufacturer of automobiles. Thus, it is possible to improve the reliability of wheel speed detection. Reference Patent Document 1: Japanese Laid-open Patent Publication No. 254985/2003.
However, in the prior art wheel bearing apparatus incorporating a wheel speed detecting apparatus, since the sensor holder 119 is arranged between a knuckle (not shown) and the outer joint member 110, it is believed that foreign matter, such as muddy water etc., would enter into the bearing apparatus through an annular space between the outer joint member 110 and the knuckle. Thus, this would detract from the detecting accuracy of wheel speed. In addition, it is also believed that foreign matter may enter and solidify on rotational parts of the wheel bearing. The dry matter would be blown off by a centrifugal force and damage surfaces of the magnetic encoder 114 and the holding portion 118. Accordingly, it is difficult to maintain the reliability of wheel speed detection for a long term.
In addition it is also believed that a suitable air gap (labyrinth) would not be formed, due to formation of a gap between the flange portion and the end face of the outer member 101, if the fitting portion 117a of the fitting cylinder 117 is press-fit obliquely or incorrectly onto the outer member 101.
It is also believed that the length of the harness 122 (FIG. 30) would be insufficient after assembly of the bearing apparatus and damaged. Foreign matter once entered into the bearing apparatus could not be surely discharged from the bearing apparatus. Accordingly, it stays in the bearing apparatus and solidified due to erroneous positioning of a draining aperture 123 of the fitting cylinder 117. If the fitting cylinder 117 is erroneously press-fit onto the outer member 101 in its circumferential direction, the holding portion 118 joined to the fitting cylinder 117 is also erroneously positioned relative onto the outer member 101. Thus, foreign matter entered and solidified on rotational parts of the wheel bearing would be blown off by a centrifugal force and damage surfaces of the magnetic encoder 114 and the holding portion 118. Accordingly, it is difficult to maintain the reliability of wheel speed detection for a long term.
Furthermore, since the holding portion 118 of the sensor holder 119 is not strictly limited in a projection amount from the end face of the outer member 101 and in a radial thickness, it is believed that the holding portion 118 will interfere with the outer joint member 110. In addition, it is believed that the holding portion 118 would be damaged when the harness 122 is taken out from the holder portion and caught by anything during transportation of the bearing apparatus. Especially in cold environments, the holding portion 118 would be liable to be damaged by an excessive load applied to the mounting portion of the harness 122 during steering of the vehicle wheels since the harness 122 would be in a frozen condition.